The power take-off unit (PTU) is used in a vehicle (e.g., commercial Vehicle passenger vehicle) to output the power to the outside. For example, in a four-wheel drive vehicle, the PTU is connected to a front engine and transmission so as to transmit the torque to a rear axle.
The PTU ring gear shaft is one of the important components of the PTU. FIG. 1 shows a schematic view of the PTU ring gear shaft in the prior art, wherein a right side end 1 is the input end which is connected to the transmission case via a coupling sleeve, a bearing is mounted to a left side end 2 so as to be fitted with the PTU case, and an intermediate flange 3 is connected to a bevel gear so as to transmit the power to the rear output shaft. In the prior art, the PTU ring gear shaft is designed to be a solid circular ring, which does not meet a lightweight requirement.
In the prior art, PTU ring gear shafts are mostly manufactured using machining methods. Firstly, a suitable tubing material or bar material is selected; then, the inner and outer sides of the material are cut and formed. Such a way of manufacturing has a high cost, a low utilization rate of material and a low production efficiency, thus making it not suitable for mass production. More importantly, this manufacturing method destroys metal streamline, thus greatly reducing the performances of elements.
In the prior art, there is also a method for manufacturing PTU ring gear shaft, in which a blank is produced by firstly cold-pressing precision molding and forging, and then precision machining. This method also has the defect of low utilization rate of material. Meanwhile, whether cold-pressing molding or forging, a high requirement is put on the mold; moreover, the mold has a very high cost and the service life of it is also not long, and meanwhile a large-tonnage press machine is required. The elements produced by cold-pressing and by forging have a poor plasticity and impact ductility as well as a large residual stress, which will result in a deformation of elements and a reduction in the resistance to stress corrosion.